How much long-duration grid-scale energy storage will be needed, and at what cost, as the share of renewable generation grows?

Projections of long-duration storage cost and deployment differ because the underlying cost trajectories are themselves uncertain: hydrogen storage costs have a learning rate broadly similar to lithium-ion batteries but described as much more uncertain, and it remains disputed whether dedicated long-duration storage or alternative flexibility options such as demand response, network expansion or flexible generation will prove the lower-cost path to a high-renewable grid.